1. Field of the Invention
The invention described herein relates to the field of aqueous systems for extreme temperature applications, especially extremely low temperature applications. The disclosed system provides an excellent base for systems for neutralizing or decontaminating chemical and biological contaminants. In this latter aspect, the invention relates to a decontaminant solution suitable for use in a variety of environments against a broad range of chemical and/or biological agents, and more particularly to a system in which the primary decontaminating agent is stabilized to provide a longer useful life.
The current invention provides an aqueous microemulsion base that is stable over a temperature range heretofore unattained, making the microemulsion useful for many applications. In particular, it can be used to provide a broad-spectrum decontaminant solution that is effective and stable over a wide temperature range. The decontaminant likewise is useful against both biological and chemical agents, and utilizes components that are not significantly ecologically disadvantageous. In addition, a means has been found to stabilize the decontaminant component itself, making the decontaminant effective for a period of time longer than that expected of other decontaminants. The current invention thus provides a decontaminant that is relatively harmless to humans and the environment and yet is effective for eliminating contamination on most surfaces.
2. Brief Description of the Art
Emulsions are useful in and of themselves for a variety of uses. Because emulsions by the nature thereof have both lipophilic and hydrophilic properties, they have the capability of “wetting” and thereby dissolving or at least suspending both lipophilic substances such as grease and hydrophilic substances that require a more polar substance for dissolution or suspension. Microemulsions are even more useful in many situations because of the greater boundary layer surface area between the lipophilic and hydrophilic components of the mixture. Because of this “dual” nature of a microemulsion, the microemulsion can be used, for example, as a rinse or wash to solubilize or suspend both polar and nonpolar liquids or other substances.
Contamination by chemical, biological, or radioactive substances, whether intentional or accidental, is of increasing concern in both military and civilian environments. Delivery systems for intentional contamination can be easy to obtain or build and difficult to detect. Also, many types of contaminants degrade only very slowly. Radioactive contamination generally must be physically removed from an area to effect decontamination. Chemical contaminations likewise must be physically removed, e.g., by flushing an area with liquids, and/or must be chemically converted to forms that are less toxic. Biological agents also can be washed away or killed by selected reagents, but many biological agents or forms thereof, i.e., spores, are highly resistant to damage and can persist for long periods of time.
As addressed herein, chemical agents (CA) specifically include but are not limited to vesicants and nerve gases. Vesicants, blistering agents that particularly affect skin and mucous membranes, are exemplified by the sulfur mustard (bis-(chloroethyl)-sulfides, commonly designated as HD), and nitrogen mustard (tris-(2-chloroethyl)-amines, commonly designated as HN-1, HN-2, and HN-3) compounds. The class of vesicants also include Lewisite (L), an arseno-ethene compound. Chemical agents also include nerve gases, the better known ones including Tabun (GA) and the phosphonofluoridates, Sarin (GB), and Soman (GD). There is additionally a class of compounds referred to as V compounds that include phosphorylthiocholines such as VX.
Biological agents (BA) primarily consist of bacteria, viruses, and fungi. These agents may be native or engineered, and include such well-known agents as anthrax. Many BAs are relatively vulnerable in the vegetative state, and can be destroyed or otherwise decontaminated through the use of common disinfectants, many of which are relatively harmless to the environment. Many BAs, however, can also exist in the form of spores. Spores can persist for long periods of dormancy, and many are vulnerable only to harsh conditions such as high heat or powerful reagents such as concentrated acids, bases, or other chemicals. Decontamination of many, especially outdoor, areas is difficult or impossible by exposure to harsh conditions, and use of concentrated reagents is often harmful to humans.
Several decontamination solutions and/or compounds have been proposed. One, Decontaminating Solution 2 (DS2) was originally used by the United States Army and contained diethylenetriamine, ethylene glycol mono-methyl ether, and sodium hydroxide. Standardized in 1960, it is no longer actively employed. While effective against CM, this solution is toxic, flammable, and environmentally hazardous. U.S. Pat. No. 6,245,957 proposes another CA decontaminant comprising a carbonate, peroxide, and alcohol mixture. This combination is described as being environmentally safe and effective “in cold weather operations.”
A decontamination formulation capable of forming an emulsion is proposed in U.S. Pat. No. 6,525,237, comprising a mixture of hydrated chloroisocyanuric acid, a selected glycol compound, a surfactant, a buffering system to maintain a pH of about 8.5 to 11, and water. In this disclosure it is stated that all of the ingredients can be premixed before being introduced to a pump and/or spraying nozzle for application, although it is preferred that the erosive and corrosive acid and buffer be added at a location after the pump. This solution is stated as being effective against all three contaminant sources by chemically neutralizing CAs, killing BAs, and encapsulating and removing radioactive agents.
A water-in-oil (W/O) microemulsion also including a peroxide/molybdate reactant system is proposed in U.S. Pat. No. 6,723,891 as effective against chemical contaminants. In this case, the microemulsion is comprised of, for example, hydrogen peroxide, a surfactant, and methylene chloride as the oil constituent (which is environmentally harmful), and butanol (as a cosolvent). This W/O microemulsion is stated as being stable in the range of from about −30° C. to about −40° C. and it is preferred to maintain the pH of the solution in the range of from 7 to 12. The drawback to this system, however, is the potential harm to personnel, materials, and the environment due largely to the negative effects of the methylene chloride.
A microemulsion decontaminant is also proposed in U.S. Patent Application Publication Number 2005/0288203. The microemulsion incorporates a solid source of peroxycarboxylic acid, which is effective against chemical agents and against vegetative biological agents. The solution also contains a germinant that causes spore BAs to convert to vegetative states, at which point they become vulnerable to the other components of the microemulsion.